This invention relates in general to ink ribbons used in shorthand machines. In particular, this invention relates to an efficient and disposable ribbon cartridge for use in shorthand machines.
Shorthand machines are commonly used to record spoken words in a visual form. For example, stenographers typically use shorthand machines to record statements made in depositions, hearings and other court-related proceedings. Shorthand machines manufactured by the assignee of the present invention have operated successfully and efficiently for many decades.
The conventional shorthand machine has a keyboard of twenty-two phonetically-related characters which, to the skilled operator, provides all combinations necessary to record words and numbers. The record produced by-the machine may be a paper tape on which the phonetic characters are printed, or the characters may be recorded on a magnetic tape medium. One example of paper recording is generally described in U.S. Pat. No. 2,319,273, which was assigned to the predecessor of the assignee of the present invention. One example of magnetic recording is generally described in U.S. Pat. Nos. 3,557,927 and 4,205,351, also assigned to the assignee of the present invention.
To record a word or parts of a word in a conventional shorthand machine, the machine operator presses an appropriate combination of the keys, and the machine mechanically prints the characters simultaneously on a paper tape, or in the case of electric recordation, combinations of electrical-pulses are recorded on a magnetic tape or disk medium. For paper tape recordation, the keys actuate associated type bars to cause the type bars to impact on an inked ribbon to print characters on the paper.
The ribbon for a shorthand machine is typically an xe2x80x9cendless loopxe2x80x9d design. The general principal of the endless loop is to utilize a single ribbon in a closed circle as described and illustrated in U.S. Pat. No. 2,319,273 (""273 patent). The entire disclosure of the ""273 patent is incorporated herein by reference.
As best shown in FIG. 5 of the ""273 patent, the ribbon 28 passes around a ribbon spool 173 and between a platen 27 and asset of type bars 73. A fabric 196 is wrapped around the core of the spool to absorb ink from the spool and impart the ink to the ribbon as it contacts the fabric. Ink is provided to the spool via openings in the top of the spool. The user must periodically replenish the ink in the spool through the openings. A pair of ribbon pressure rolls 222 and 223 force the ribbon against the ink-filled fabric on the spool. A mechanical connection (described in detail at col. 11, line 16 to col. 12, line 27) between the spool and the keys rotates the ribbon spool whenever keys are pressed, thereby advancing the ribbon around the spool (via pressure rolls) and through the print area. The platen 27 holds paper for printing, and the type bars 73 are each associated with one of the keys. When a key is pressed, the associated type bar is urged toward the platen, thereby urging the ribbon into contact with the paper on the platen for printing characters on the paper.
In contrast to the typical synthetic typewriter ribbon, which is inked and printed once, the endless loop ribbon is made from an absorbent fabric which is continuously cycled through the print area and replenished with ink. Thus, a given area of the endless loop ribbon is printed on several thousand times during the useful life of the ribbon.
Although a significant amount of a shorthand machine""s functions are controlled electronically, many functionsxe2x80x94such as ribbon advancement, print hammer movement and platen advancementxe2x80x94are controlled mechanically, or at least provided with a mechanical (manual) mode. Having mechanical functions allows the shorthand machine to be used in places where electrical service is non-existent, inconvenient, or unreliable. Additionally, the mechanically driven functions typically make less noise than the electrically driven functions. This is important because in most applications, particularly in court reporting, it is essential that the shorthand machine operates as quietly as possible.
Because the endless-loop ribbon is advanced mechanically by pressing the keys, it is important to minimize the force required to advance the ribbon. Thus, it is advantageous to provide a minimum amount of friction between the moving parts of the advancing mechanism so that the force required to depress the keys is also minimized.
The Xscribe Corporation has sold an endless-loop-based cartridge for use with its Stenotype(copyright) family of shorthand machines. The Stenotype cartridge includes a relatively long ribbon which is folded at right angles to create a 90xc2x0 change of direction for the ribbon. The ribbon is advanced through the cartridge by passing between and engaging a drive gear and an idle gear. The idle gear transfers ink to the ribbon by rubbing against a stationary ink-holding foam stem which acquires its ink from an apparently rectangular and stationary ink reservoir.
Several problems are associated with the Stenotype(copyright) cartridge, the most important of which is the amount of force required to advance the ribbon through the cartridge. For example, the contact between the stationary ink stem and the idle gear creates a significant amount of unwanted friction in the advancing mechanism. Additional friction is generated when the ribbon is pulled through its 90xc2x0 bend. Also, the extremely long ribbon is confined within the relatively small Stenotype(copyright) cartridge by providing a holding area for the ribbon inside the cartridge. The ribbon is literally bunched and packed into the holding area and must be pulled through this area by the single drive/idle gear combination. Thus, the Stenotype(copyright) machine includes a motor driven ribbon advancing mechanism (electric mode) in addition to a mechanical key-driven ribbon advancing mechanism (manual mode). In the manual mode, the force required to depress the Stenotype""s keys could become unacceptable for the operator during extended use.
Additionally, the Stenotype cartridge""s ribbon tends to have heavy ink in some areas and light ink in other areas, resulting in a rather messy cartridge and inconsistent print quality. This is apparently due to the fact that the ribbon is bunched in the holding area such that ink is allowed to migrate randomly from one portion of the ribbon to another. Also, the stationary ink stem is itself easily saturated with ink from the ink reservoir, resulting in a non-uniform transfer of ink to the idle gear and further contributing to inconsistent print quality.
Thus, it is an object of the present invention to provide an endless-loop ribbon cartridge that takes full advantage of the benefits associated with utilizing a cartridge. It is also an object of the present invention to provide an endless-loop ribbon cartridge that does not significantly increase the amount of force required to depress the shorthand machine""s keys. It is a further object of the present invention to provide a ribbon cartridge that supplies an even distribution of ink to the ribbon. Additionally, it is an object of the present invention to provide a ribbon cartridge having a relatively long life and requiring little or no maintenance.
The present invention is directed to a disposable ribbon cartridge for use in a shorthand machine. The cartridge comprises a housing having an endless loop ribbon extending through a prescribed pathway in the housing. An advancing mechanism advances the ribbon through its prescribed pathway, and also transfers ink from a movable ink reservoir to the ribbon. The ink reservoir is preferably made from a reticulated and felted polyurethane foam having specific wicking properties.